1. Field of the Invention
The present invention relates to techniques for protecting rights associated with digital content.
2. Description of the Related Art
In recent years, a variety of digital content including images, video, documents, audio, game programs, and other software items have been provided to users from various content providers. In provision of such digital content, a technique referred to as DRM (Digital Rights Management) is often utilized to protect rights, such as copyright, of the content providers.
One common system for implementing the DRM technique utilizes electronic tickets. In this system, use of digital content distributed to users is restricted by, for example, encryption. Such use restriction is sometimes called “encapsulation”. When a user wishes to use encapsulated digital contents (hereinafter simply referred to as capsules), they separately acquire an electronic ticket including information, such as a key, necessary for lifting the use restriction. An electronic ticket is sometimes referred to as a license. To use a capsule, a user accesses to a right manager server, and completes user authentication and ticket purchasing processes in order to acquire an electronic ticket.
For implementing a DRM system using electronic tickets, applications handling the capsules must generally have a function providing capability of dealing with use restriction (DRM function), such as decrypting digital content and operation restricting processing in accordance with use restrictions.
Applications having a plug-in mechanism (such as Acrobat (trademark) available from Adobe Systems Inc. in the United States) may later incorporate the DRM function into the main frame of the application. A related art suggests use of a plug-in technique for incorporating the DRM function into an application. As another related art, a DRM method using electronic tickets is also known.
However, the protection scheme using electronic tickets cannot be applied applications with neither a DRM function nor a plug-in mechanism. For example, “Word”, a word processing application, or “Excel”, a spreadsheet application, both produced by Microsoft Corporation, do not have a plug-in mechanism for DRM, and therefore data protection through DRM using electronic tickets cannot be applied through these applications.